In roles from police commissioner to street cop, the Reagan clan has always brushed up against politics on Blue Bloods. But in the drama's 13th season, Trial Bureau chief Erin Reagan (Bridget Moynahan) is going for full immersion: She makes a run for Manhattan district attorney against her boss, DA Kimberly Crawford (Roslyn Ruff)!

Bridget Moynahan: A frustrated Jamie [Will Estes] comes to see Erin because a man he arrested is back on the streets, which leads to him being in the line of fire. Erin feels guilty that her office keeps putting dangerous people back out there, but this time it hits home.

Which brings up the question, how does being the police commissioner's daughter affect the race?

Erin has to come out of the gate with opinions — that may or may not be in line with the police department — so that the voters can see she's not under the commissioner's thumb.

What does her dad, PC Frank Reagan (Tom Selleck), think about her decision to run?Frank puts out a statement without communicating with Erin, and she's very much taken by surprise and has to figure out his true motive.What are you looking forward to in this new chapter for Erin?The different characters they'll bring in to work on her campaign.

There are good scenes with Crawford, who's not shy about getting down and dirty in a fight.And Erin's ex-husband, Jack Boyle (Peter Hermann), is back.He offers to introduce her to somebody with political and financial support. That opens the door to conversations that bring them closer, but now that's she's running for office, I think she's waiting. Your private life is exposed no matter what it is.They can't hide their chemistry.It's a rare moment on Blue Bloods when you have a flirtation, so I'm happy we provide that bit of spark!